1. Field of the Invention
This invention is directed to improving properties of coals and, in particular, to improving yields and physical characteristics of coal liquefaction distillates and bottoms.
2. Description of the Prior Art
Much work has been done in recent years to make useful liquids and gases from coal. Various types of liquefaction processes have been developed, such as solvent refining, direct hydrogenation with or without a catalyst, catalytic or non-catalytic hydrogenation in the presence of a non-donor solvent, and catalytic or non-catalytic liquefaction by the donor solvent method. Exemplary of the solvent hydrogen donor liquefaction process is U.S. Pat. No. 3,617,513.
In an effort to increase liquefaction yields, a number of ancillary processes have been developed, such as pretreatment of coal prior to the liquefaction process or post-treatment of products derived from the liquefaction process, e.g., liquefaction distillates, coal liquids and bottoms. Exemplary of pretreatment processes is U.S. Pat. No. 4,092,235, which discloses acid-catalyzed Friedel-Crafts C-alkylation or C-acylation of coal to increase the yield of products from coal liquefaction. The introduction of aliphatic hydrocarbon radicals or acyl radicals, including carbon monoxide, into the coal structure is believed to permit a greater quantity of the coal to undergo liquefaction at suitable liquefaction conditions. The alkylation or acylation reactions, which may be conducted in the presence or absence of added or extraneous catalysts, take place at carbon sites.
Many of the C-alkylation and C-acylation processes require a considerable amount of alkylating or acylating agent in order to accomplish their purpose. Further, during the subsequent coal liquefaction process, phenols present in the coal are cleaved to produce water. In liquefaction processes employing hydrogen, an excessive use of hydrogen thus occurs.